1. Field of the Invention
The present invention relates to a valve lifter finger follower for an internal combustion engine.
2. Background Art
Valves for internal combustion engines are generally opened and closed to allow for the intake and exhaust of gases in cylinders of the engine. Valves are operated by various valve lifter mechanisms including rocker arms and roller finger follower assemblies. Roller finger follower assemblies are well suited to overhead cam engines and also V-type engines. Timing valve opening and closing is important to maximize fuel efficiency, assure complete combustion, and maximize engine output. Adjusting valve timing can lead to improvements in fuel economy, engine emissions, torque and idle quality.
Many different approaches have been proposed for providing adjustable valve timing. Some prior art approaches include independent lifter control for each cylinder by means of electrical solenoids or by changing the pivot point for a rocker arm. Various other approaches have also been proposed.
There is a need for a system and apparatus for providing adjustable valve timing wherein the valve timing may be adjusted in a synchronized manner to minimize variation of timing from cylinder to cylinder. There is also a need for a simple and effective valve timing adjustment mechanism that may be used with intake or exhaust valves. There is also a need for a valve timing adjustment mechanism that is amenable to dual overhead cam and single overhead cam applications.
The above problems and objectives are addressed by the present invention as summarized below.
According to one of the aspects of the present invention, a valve timing system for an internal combustion engine is provided wherein a finger follower arm is attached to a camshaft contact roller in an adjustable manner that permits the roller to be located within a range of positions along the length of the finger follower arm. The roller is supported on the finger follower arm to contact a rotating cam on a camshaft. A linkage is provided for adjusting the position of the camshaft contact roller and thereby change the valve timing of the internal combustion engine.
According to another aspect of the invention, a roller finger follower assembly for an internal combustion engine is provided for an internal combustion engine having a camshaft. A lobe of the camshaft is rotated in accordance with the operating cycle of the internal combustion engine and contacts the roller finger follower assembly to open and close its associated valve. The roller finger follower assembly includes a base arm that is pivotally secured to a pivot connection and has a finger that engages the valve. A roller carriage supports a roller that is adjustably secured to the base arm with the roller being disposed between the pivot connection and the point at which the finger contacts the valve. The roller is positioned to contact the cam lobe as it is rotated by the camshaft. An adjustment link is provided for shifting the roller carriage relative to the base arm to cause the roller to contact the lobe of the camshaft within a range of angular positions relative to the camshaft.
According to another aspect of the invention, a finger follower assembly is provided for an internal combustion engine having at least one valve that is opened and closed in a timed manner to port combustion gases for the combustion chamber of the internal combustion engine. The internal combustion engine has at least one camshaft having at least one cam lobe that is rotated by the camshaft in accordance with the operating cycle of the internal combustion engine. The cam lobe contacts the roller finger follower assembly periodically to open and close the valve. The roller finger follower assembly includes a lash pin having a cam portion defining a contoured surface. A first linkage connector and a second linkage connector are provided on opposite ends of the lash pin. An arm is secured to the lash pin at a first end. The arm has a valve engaging finger that engages the valve at a second end of the arm opposite the lash pin. A roller is mounted on the arm between the lash pin and the finger and is positioned to be periodically contacted by the lobe on the camshaft that causes the valve to open and close periodically. First and second linkages are operatively connected to the roller to adjust the position of the roller on the arm. A lash adjuster is attached to the engine and is positioned to engage the lash pin. The lash adjuster is secured to the engine and is adjustable to change the point at which the contoured surface of the lash pin contacts the lash adjuster. Rotation of the lash pin causes the linkages to move the roller and also changes the point at which the lash adjuster contacts the contoured surface to thereby provide a secondary lash adjustment.
According to another aspect of the invention, the finger follower arm comprises a base arm and a roller carriage to which the camshaft contact roller is rotatably secured. The roller carriage is shiftably attached to the base follower arm that may be provided in a form of a track and track follower.
According to another aspect of the invention, the linkage may further comprise an adjustment link and an adjustment cam. The adjustment link is secured on a first end to the adjustment cam and on a second end is secured to the camshaft contact roller. A camshaft contact roller is secured to the finger follower arm and is engaged by a second end of the adjustment link to move the roller carriage relative to the finger follower arm.
The linkage may also include a lash pin that engages the finger follower arm wherein the lash pin is rotatable relative to the finger follower arm. The lash pin may be rotated to rotate the adjustment cam relative to the finger follower arm to cause the adjustment link to move the cam shaft contact roller.
According to another aspect of the invention, the camshaft contact roller is moveably mounted on the finger follower arm to cause the lift of the valve to occur at different timing positions relative to the rotating cam.
According to another aspect of the invention, the lash pin may include a contoured section that contacts a lash adjuster attached to the engine thereby permitting simultaneous adjustment of valve timing, valve lift and lash control. The lash adjuster may also include a friction cap that is interposed between the lash pin and lash adjuster to minimize wear of the lash pin and lash adjuster.
These and other advantages and aspects of the present invention will be apparent to one of ordinary skill in the art in view of the attached drawings and following detailed description of the embodiments of the invention below.